Thames Valley Police and one of the force’s firearms instructors are due to be sentenced today after he shot and almost killed a civilian colleague.

Pc David Micklethwaite, 52, who had failed part of a gun training course, mistakenly loaded a powerful Magnum .44 revolver with a live round from an old Quality Street tin, during a weapons awareness tutorial.

He then pulled the trigger while pointing it at phone operator Keith Tilbury at the police’s Headquarters North in Kidlington, causing life-threatening injuries.

The 51-year-old underwent five hours of surgery to his bowel and kidney, and also suffered lung and liver damage.

Micklethwaite and the police force have admitted breaching health and safety rules.

The force faces an unlimited fine at the hearing at Southwark Crown Court in London.